An atmometer is an instrument used or measuring evaporation. Atmometers have been known for some time, and can either be of a design whereby measurement of the rate of evaporation of water from a wet surface is determined or measurement of the rate of evaporation of water through a porous surface is determined. In the past, problems have been experienced in obtaining accurate and reproducible readings from atmometers, and it has been proposed in the scientific literature that existing atmometers are susceptible to windy conditions, causing inaccuracies in readings.
It has become increasingly important to simulate and estimate vapour loss through transpiration in plants, particularly plants subjected to, or growing in, dry environments. Transpiration from a plant leaf is a two-stage process. Moisture first evaporates from a wet surface of parenchyma cells within the leaf, which cells are surrounded by air spaces necessary for exchange of gasses during photosynthesis. Typically water evaporated into the small amounts of air in these spaces is at saturation vapour pressure for the temperature of the leaf. In the second stage of this process, the saturated air diffuses from within the leaf through the stomatal openings in the leaf surface and mixes with ambient air to be removed by wind action.
It would be advantageous if an instrument could be provided that at least partially simulates this process to provide some indication of the evaporation of water in agricultural environments.